Electric fuse



Feb. 11, s R s JR 2,231,599

ELECTRIC FUSE Filed Jan. 11, 1939 Fig. l

INSULATION Inventor: Sidney R. Smith,Jn,

' His Attorney.

Patented Feb. 11, 1941 UNITED STATES 2,231,599 ELECTRIC FUSE Sidney R. Smith, Jr., Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application January 11, 1939, Serial No. 250,374

4 (Ilaims. (Cl. 200-117) The present invention relates to electric fuses and more particularly to so-called secondary fuses which are suitable for such purposes as protection of transformers from secondary faults, isolation of service entrance faults, and banking of transformer secondaries.

The invention has for a principal object the provision of an improvedand simplified form of secondary fuse which requires no separate in- 10 sulating support and is adapted for, but not necessarily limited to, outdoor installations such as on overhead distribution lines in conjunction with strain insulators; which has such low construction, installation, and refusing cost as to render it eminently practical and economical for the purposes above stated; and which, upon fuse operation, functions so as to insure complete electric isolation of the fuse holder from at least one of the conductors connected therewith while giving readily observable indication of fuse operation.

More specific objects and-the details of that which I consider to be novel and my invention will become apparent from the following description and the claims appended thereto, taken in conjunction with the accompanying drawing in which Fig.1 shows the details of construction of a device embodying the invention and illustrates one way in which the device may be applied to an electric line, while Fig. 2 illustrates the positioning of the parts of the device of Fig, 1 after fuse operation.

The device of the present invention is suitable for application to electric lines in various ways depending upon the location at which fused protection is desired, but for purposes of example,v

the device is shown mounted on an electric line in conjunction with a common form of strain insulator, indicated at I. This insulator serves to join mechanically two line conductors II and I! which are fastened to the insulator in a well known manner so as to leave'the ends II and II, respectively, of the conductors free for connection purposes. The two conductor ends are employed as the sole means of support and electric connection of the fuse device of the present invention.

I As will be seen from the drawing, my improved fuse device has a fuse holder or housing comprising an elongated tube ii, of fibrous or other suitable insulation material, upon the opposite ends of which are mounted. metal terminal caps IO and I1. Cap I 8 is screw-threaded on to the tube so as to be fixed relative thereto and to provide a weather-tight closure for the corresponding end of the tube. Cap I 1 fits slidably over the other end of the tube in such manner that it may be ejected from the tube, although it normally provides a relatively tight closure. Within the bore of tube I5 is a fuse link which may be of any desired form, but which is illustrated as com- 5 prising terminal shanks i8 and I9 joined by a fusible element 20 and a strain wire 2|. Terminal shank I8 is formed with a buttonhead cap 22 which is securely anchored by means of terminal cap IS. The other terminal shank, l9, has a flexible stranded cable extension 23secured thereto, which extension is threaded through an opening 24 in the end of terminal cap H. In order to retard the entrance of moisture into the fuse tube, opening 24 is made of such small size as just to accommodate extension 23.

Caps l6 and 11 are formed with lateral projections 25 and 26 respectively, each of which carries a slotted clamping bolt 21 and clamping nut 28. A bared portion of the free end l3 of line 20 conductor II is clamped in the slot of the bolt 2'! carried by terminal cap It so as to support and provide electric connection to the left-hand end of the fuse device, as viewed in the drawing, Similarly, a bared portion of the free end I! of line conductor l2, together with the end of fuse link cable extension 23, is clamped in the slot of the bolt 21 carried by cap l'lat the right-hand end of the fuse device. With the end of cable extension 23 thus anchored, the fuse link serves to maintain cap H on the end of the fuse tube, and the fuse link is maintained under tension by a compression spring 30 coiled around the fuse tube. One end of this spring is anchored to the tube in any suitable manner, as by means of a pin 3|, while the other end of the spring presses against the inner end of cap l1. With the fuse link intact and the parts in their relationships as just described, the fuse device provides electric connection between line conductors I i and I2.

Upon rupture of fusible element II and strain wire 2| due to excess current, spring 30 is released and becomes operative to impel terminal cap I! from the end of fuse tube It. This aids in drawing out the arc within the tube so as to insure a quicker extinction thereof, and permits the fuse tube to swing downwardly to its position indicated in Fig. 2 wherein it is suspendedfrom the free end ii of line conductor ll. Thus the fuse tube is isolated from terminal cap I! and line conductor l2 so that there is no danger ofleakage thereacross with resultant undesirable carbonization of the tube.

From the foregoing it will be seen that my improved fuse device embodies a relatively small number of parts of simple construction and arrangement, which parts however are capable of effectively interrupting the circuit between line conductors II and I2 upon occurrence of an overload or short-circuit. Also, by separation of terminal cap I! from the fuse tube, the device gives a clearly observable indication of fuse operation while insuring against electric leakage across the fuse tube when the parts are in operated condition. Further, and of importance, is the fact that in addition to the advantages previously mentioned, the device is of such simple and low cost construction that it recommends itself for use in remote rural installations where reliability and economy are prime considerations.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A line suspension fuse comprising an insulating fuse tube, a pair of terminal caps telescoped respectively over the opposite ends of said tube in closing relation thereto and each having conductor clamping means for attachment to an electric line conductor in a manner to support the fuse directly on such conductor, one of said caps being fixedly secured to said tube, the other of the caps and its associated conductor clamping means being relatively loosely mounted on the tube and being arranged to be impelled ofi of the tube upon fuse operation so as to effect complete isolation of the tube from a conductor connected withsaid other cap, and a fuse link in said tube, electrically connected between said caps and mechanically attached to said other cap so as normally to hold the latter in closing relation to the end of the tube.

2. A line suspension fuse comprising an insulating fuse tube, a terminal cap telescoped over and fixedly secured to one end of the tube, a second terminal cap slidably telescoped on the other end of the tube, said caps each having a clamp for attachment thereof to an electric line con ductor in a manner to support the fuse directly on such conductor, a fuse link electrically connected between said caps and mechanically attached to said second cap so as normally to hold the latter in closing relation to the end of the tube, and means operative upon rupture of said fuse link to impelsaid second cap and its associated clamp off of the end of the tube so as to isolate the tube from a conductor connected with said second cap.

3. A line suspension fuse comprising an insulating fuse tube, a terminal cap fixedly secured on one end of the tube, a second terminal capslidably telescoped on the other end of the tube, said caps each having a clamp for attachment thereof to an electric line conductor in a manner to support the fuse directly on such conductor, a fuse link in said tube electrically connected between said caps, one end of said link being anchored relative to said tube and the other end of the link being mechanically attached to said second cap so as normally to hold the latter in closing relation to the end of the tube, and a compression spring in surrounding relation to the tube with one end of the spring anchored to the tube and the other end of the spring bearing against said second cap so as to impel said second cap and its associated clamp off of the end of the tube upon rupture of said link, thereby completely to disconnect said tube from a conductor connected with said second gap.

4. A line suspension fuse comprising an insulating fuse tube, a fuse link in said tube having one end anchored relative to the tube, a pair of terminal caps telescoped respectively on the opposite ends of said tube and each having an integral extension projecting laterally to one side of the tube, clamps carried respectively by said extensions for attachment of said caps respectively to conductors of an electric line in a manner to support the fuse directly on such conductors, one

of said caps being fixedly secured to said tube, the other of the caps and its associated clamp being slidably mounted on the tube and being held normally in closing relation to the end of the tube by attachment of the other end of said fuse link to said other cap, and a coiled compression spring disposed in surrounding relation to said tube and operative upon rupture of said fuse link to impel said other cap and its associated clamp from the end of the tube so as to disconnect the tube from a conductor connected with said other cap.

SIDNEY R. SMITH, JR. 

